Heat 1 tablespoon of butter in a large skillet over medium heat.
Add the sliced mushrooms and don't touch them for 3-4 minutes.
Flip and continue to cook until golden brown, about 2-3 minutes.
Add the minced shallot, then cook, stirring often, for 2 minutes.
Add the minced garlic and cook, stirring constantly, for 1 minute.
Season with sea salt and freshly cracked pepper, to taste. Pour the mushrooms into a bowl and set aside.
In a bowl, season the flour with garlic powder, some sea salt & freshly cracked pepper to taste; mix until well combined.
Whisk eggs until well combined in a separate bowl.
Cut the bottom few inches off the chicken breast. Cut each remaining portion of chicken breast in half, lengthwise. Place plastic wrap over the chicken on the cutting board and pound with a mallet until about ¼-½ inch thick.
Heat two tablespoons of olive oil in a large skillet over medium-high heat.
Dip the chicken lightly in the seasoned flour, next dip it into the whisked egg, and lastly dip it back into the flour before placing it in the hot oil in the skillet; repeat with the remaining chicken, cooking in batches if needed.
Cook the chicken undisturbed until golden brown, about 4-5 minutes, then flip and cook until golden brown and cooked through, about 3-4 minutes.
Remove from the skillet and place on a plate lined with paper towels. Cover loosely with a foil tent.
Add a tablespoon of butter to the large skillet, then whisk in the flour until well combined.
Add the wine and whisk until it thickens, about 1 minute.
Slowly whisk in the chicken broth and lemon juice. Simmer for 2-3 minutes.
Add the mushrooms and their liquids to the sauce; mix well.
Whisk in the tablespoon of butter, then taste and season with sea salt and freshly cracked pepper to taste. Add more lemon if needed.
Place the chicken on a serving platter, then drizzle with mushroom sauce and sprinkle the top with fresh parsley.